The invention generally relates to control systems and methods for a dry feed system to pneumatically convey a solid fuel to a container such as a gasifier.
The dry feed system generally has a feed tank and a plurality of pipelines. The feed tank receives the solid fuel and a carrier gas through the pipelines and outputs a solid-gas mixture. The pipelines have a mixture pipeline connecting the feed tank and the gasifier for conveying the solid-gas mixture. The stable and controllable solid fuel flow has significant influence on the gasification performance of the gasifier. Therefore, control systems are used for controlling the solid, fuel conveyance. For the control systems, solid mass flow rate (referred to as “solid flow rate” hereinafter) in the solid-gas mixture is a significant parameter for monitoring and adjusting the solid fuel flow.
In a conventional control system, the pressure of the feed tank (referred to as “feed tank pressure”) is adjusted to control the solid flow rate. In another conventional control system, solid control valves are distributed and installed on the mixture pipeline. The solid control valves adjust the solid flow rate by responding to the control signals based on the real time solid flow rate. Although the latter conventional control system can achieve a more stable solid fuel flow than the former one, the solid control valves are usually required to be made of a wear resistant material since the solid fuel may cause significant wear abrasion to the solid control valves. As a result, the production cost of the solid control valves is higher due to these material requirements.
Therefore, there is a need to provide improved and economical control systems and methods that can control the solid fuel stably conveyed.